The present invention relates generally to computer systems, and more specifically to a system for controlling cursor movement on a computer display screen.
Graphical computer displays are very helpful in interpreting many types of information which could otherwise be difficult to understand. With the advent of bit-mapped graphics capabilities, high quality computer graphics displays are becoming common. Automated design systems, data interpretation systems, and the like can be operated by displaying graphs or drawings on a computer screen, and a user can make changes or inquiries by moving a pointing device around on the display.
A user can point to objects or locations on the graphics display by moving a pointer, often referred to as a cursor, on the screen. This is often done by physically moving an optical or mechanical device such as a mouse, joystick or trackball. Movement of the physical device is detected by the computer system, and the cursor is moved on the display in a corresponding manner.
In many cases, the computer displays are representations of three-dimensional objects or data. What is shown on the display is actually a two dimensional projection of a three-dimensional structure stored within the computer system. When it is desired to point at various parts of the three-dimensional structure being displayed, it is necessary to move the cursor in three dimensions. In many applications, the mapping of two dimensional movements of the physical positioning device onto the two dimensional display gives ambigious information as to the three dimensional location of the cursor. Thus, there must be some method for entering physical cursor movement information so that the display system can detect motion in three dimensions, typically an X, Y, Z coordinate system.
Currently, three dimensional cursor movement control is provided by entering three separate signals into display system. These symbols may be generated, for example, by separate X, Y and Z controls, or a control indicating motion in a plane, such as a mouse or joystick, augmented by a separate control for the third dimension. Therefore, mouse movement can be used to indicate position in the X-Y plane, with a separate dial control indicating movement along the Z axis.
It would be desirable to control three-dimensional cursor movement using a standard two-dimensional physical control device which is familar to computer system users. It would also be desirable for such a control device to be used for unambiguous three dimensional cursor movement in such a manner that the correspondence between movements of the physical device and the cursor on the display screen is intuitively natural.
It is therefore an object of the present invention to provide a two-dimensional physical input device which allows three-dimensional cursor control on a computer display.
Therefore, according to the present invention, a two-dimensional physical input device provides an input signal to an interpreter for a computer display system. The interpreter system logically divides the plane of movement into six regions which correspond to movement in the positive and negative directions along the three coordinate axes. These regions are positioned so that movement of the input device in a direction which approximates the angle of a major axis as shown on a computer display causes cursor movement along that axis.
The novel features which characterize the present invention are defined by the appended claims. The foregoing and other objects and advantages of the present invention will hereafter appear, and for purposes of illustration, but not of limitation, a preferred embodiment is shown in the accompanying drawings.